The present invention relates to a computer mainframe signal monitoring system which uses a large scale integrated circuit to catch the major signals of the mother board such as address bus signal, data bus signal, control bus signal, and regular I/O signals, and then to send the caught signals to a driver IC, causing it to drive respective LEDs.
When a computer is controlled to execute a software program or to draw a complicated drawing, it may break down. However, the operator may not know the sudden failure of the computer, and a lot of time may be wasted in watching the display. There is known an inspection card designed for inspection the operation of the mother board. When in use, the shell of the computer must be opened so that the inspection card can be installed in the mother board to detect its circuit. This inspection card is small, and the user needs to watch the LEDs with much effort.